Diogenes Laërtius divides the philosophy of the Greeks into the Ionic, beginning with Anaximander, and ending with Theophrastus (in which class he includes the Socratic philosophy and all its various ramifications); and the Italian, beginning with Pythagoras, and ending with Epicurus, in which he includes the Eleatics as well as Heraclitus and the Sceptics. His work is the chief source of information we possess concerning the history of Greek philosophy and is the foundation of nearly all modern treatises on that subject.